#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>


int bit(int n)
{
	if (n <= 2)
		return 1;
	else
		return (bit(n - 1) + bit(n - 2));
}

int main()
{
	int n = 0;
	scanf("%d", &n);
	int ret = bit(n);
	printf("%d\n", ret);

}